The invention relates to a screw capable of temporarily holding a screw such as bolts, screws or the like without falling off a part being clamped, and clamping a part being clamped with an excellent sealing property.
Conventionally, in the case of mounting a screw, such as bolts, screws or the like, on a part being clamped and temporarily holding the same thereon without falling-off, mounting of the screw is performed by, for example, first inserting a screw shank 1 of the screw through a screw insertion hole 3 provided on the part being clamped 2 such as an automobile""s interior equipment, brackets or the like, as shown in FIG. 8 and then fitting a washer 4 of synthetic resin onto a cylindrical-shaped portion 5 below a neck of the screw by manual work. However, fitting of the washer 4 with manual work requires a large amount of manhours which increases the cost of assembly.
Also, when a screw temporarily held on a part being clamped 2 is to be clamped to a mount member 6 such as a cover or the like as shown in FIG. 9, the part being clamped 2 is first set in a desired location on the mount member 6 and the screw is threaded by rotating a bold after the screw is made to abut against a location of use, that is, an inlet of a female thread portion 7 of the mount member 6. However, since the washer 4 is mounted on a cylindrical-shaped portion 5 above a male thread 8 on a screw shank 1, a release hole 9 having a length corresponding to the length of the male thread 8 plus the length of the washer 4 is needed to be provided above the female thread portion 7, with the result that it is necessary to correspondingly make the cover thick, which will make the cover thick and heavy.
Further, there is a prior art, in which a falling-off preventive member 19 of a resin is fixed to a tip end of a screw 1, as shown in FIG. 10A. However, since such fixed falling-off preventive member 19 can not move along the male thread 8 of the screw 1 during the clamping, it had serious shortages. When the diameter of the prepared hole in the part being clamped is going larger, the length of the elastic blade portion 14 become longer and thereby the length of the falling-Off preventing member 19 also become longer, as shown in FIG. 10B.
Japanese Utility Model Publication No. 5365/1996 has been published on a prior application filed by the applicant of this application, and discloses the provision of an annular recess for causing a temporary holding member to be embedded between a threaded portion and a neck portion of a screw. However, such temporary holding member is an insert molding, which is free of rotation about a screw shank of the screw, and so neither teaches nor suggest the invention of this application.
Also, in the case where a prior art screw is used to perform bolt-clamping of a part being clamped 2 to a mount member, a screw seat surface 11, with which a back surface of a screw head 10 comes into contact, is not fully sealed, so that moisture content such as rain water or the like sometimes permeates clamped portions to generate corrosion such as rust. To cope with this, there is the need of mounting a rubber washer on the screw seat surface 11 to improve the sealing property, thus causing a problem that the number of parts increases and the assembly work becomes troublesome.
The invention has been thought of to solve the above-mentioned prior problem and to provide a screw capable of simplifying an assembly work and shortening a release hole for causing the screw to abut thereagainst and of clamping a part being clamped with a high sealing property.
To solve the above-mentioned problem, a screw according to the invention comprises a temporary holding member provided on a screw shank for temporarily holding the screw on a part being clamped, the temporary holding member being a molding of plastics formed on an intermediate, outer periphery of the screw shank and comprising elastic blade pieces extending radially and provided on an outer periphery of a short cylinder portion having a female thread portion matching a male thread of the screw shank 1.
Elastic blade pieces of a temporary holding member provided on a screw of the invention extend radially on an outer periphery of a short cylinder portion and are provided on an intermediate, outer periphery of the screw shank. A largest portion of the entire elastic blade pieces has a slightly larger diameter than an inner diameter of a screw insertion hole provided in a part being clamped. The elastic blade pieces can be press fitted into the screw insertion hole due to their elasticity, but it will not return back from the screw insertion hole when once inserted, and so the screw is free from naturally falling off the part being clamped. Also, the temporary holding member is provided in a location at an intermediate portion of the screw shank and as downward as possible, whereby the length of the release hole can be significantly shortened and so a mount member such as a cover or the like can be made small in thickness and lightweight.
Also, when the screw of the invention is used to integrally clamp a part being clamped to a mount member, the temporary holding member is collapsed and deformed, and a part of plastics, which constitutes the temporary holding member, fills into an air gap between the screw shank and the part being clamped and the mount member and bites into interfaces between the male thread and the female thread portion, so that sealing is made more complete, as compared with the prior art, and clamping of the part being clamped can be made.